<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>显示和隐藏</title>
</head>
<style>
    .dog {
        /*display: block;*/
        display: none;
        width: 200px;
        height: 200px;
        background-color: red;
    }

    .cat {
        width: 200px;
        height: 200px;
        background-color: gray;
    }
</style>
<body>
    <div class="dog">dog</div>
    <div class="cat">cat</div>
</body>
</html>